Coronary heart disease (CHD) causes almost as many deaths in women as it does in men, with approximately 90% of the deaths in women occurring after the age of 50. There are substantial increases in CHD risk factors at the time of the menopause, especially increases in total cholesterol and low density lipoprotein cholesterol (LDLc), that may well contribute to the increased risk of CHD. In the Healthy Women Study, LDLc increased by 3 mg per year in postmenopausal women; there was almost a 25 mg difference between LDLc in premenopausal women aged 42-45 and those aged 52 and two years postmenopausal. The aim of the proposed project is to test the hypothesis that the increase in LDLc at the time of the menopause can be ameliorated or prevented by an intensive dietary intervention. We propose to recruit 500 premenopausal women, aged 44-50, and to randomly assign them to an Assessment Only Control Group or to a Dietary Intervention Group. The aim of the Dietary Intervention will be to reduce dietary fat to <25% of calories, saturated fat to <7%, and cholesterol to <100 mg and to produce weight loss in those who are overweight and prevent weight gain in others. All women will be reassessed at months 6, 18, 30, 42, and 54. The primary outcome of interest is LDLc. The interventions will also be compared to determine a) if the dietary intervention can prevent the decrease in HDL2c and the weight gain observed at this period of a woman's life; b) whether dietary intervention affects the age of menopause or the percent of women using hormone therapy or having hysterectomy, and c) whether the dietary intervention has adverse effects on menopausal symptomatology, endogenous hormones, and bone mineral density. This would be the first clinical trial to test whether the rise in cholesterol seen in menopausal women can be prevented by non- pharmacological intervention. If successful, this clinical trial could have major effects on the number of women requiring medical intervention for hypercholesterolemia and decrease arteriosclerosis and coronary heart disease.